The Saccharomyces cerevisiae GAL80 gene ( SGDID:S000004515 ) is a negative regulator of the Saccharomyces cerevisiae GAL4 transcriptional activator. A dimer of GAL80 binds to a GAL4 dimer, such that although GAL4 can still bind the UAS sequence it can no longer activate transcription (adapted from FBrf0233764). The C-terminal 30 amino acids of the GAL4 gene are required for its interaction with GAL80 (PMID:3297349). GAL80 can thus be used to further refine the expression pattern of a gene of interest expressed using the UAS-GAL4 binary expression system, where a transgene or modified endogenous locus encoding a GAL4-based 'driver' is combined with a second transgene or modified endogenous locus in which the target gene of interest is downstream of UAS sequences (reviewed in FBrf0233764, FBrf0216478). GAL80 can potentially be used to suppress any binary expression driver or split system hemidriver that contains the interacting C-terminal portion of the GAL4 gene.